Summary:A new study uncovers a molecular connection between vitamin B12 and multiple sclerosis (MS). The study identifies a key role of astrocytes and the brain’s vitamin B12 carrier protein, transcobalamin 2, in this link.
Findings show that the MS drug fingolimod enhances the brain’s B12 uptake, potentially improving MS treatments by reducing neuroinflammation and neurodegeneration.
This discovery not only underscores the importance of B12 supplementation in MS but also opens new pathways for future therapies in neuroinflammatory and neurodegenerative diseases.
Key Facts:
- The study reveals that fingolimod, an MS drug, regulates B12 communication pathways in astrocytes, enhancing B12 uptake in the brain.
- Lower levels of CD320 or dietary B12 restriction were found to worsen MS in animal models.
- The research suggests the potential for brain-targeted B12 formulations and extends the understanding of B12’s role in neurodegenerative conditions.
Source: Sanford Burnham Prebys
For decades, scientists have noted an intriguing similarity between a deficiency in vitamin B12 – an essential nutrient that supports healthy development and functioning of the central nervous system (CNS) – and multiple sclerosis (MS), a chronic disease in which the body’s immune system attacks the CNS and which can produce neurodegeneration.
Both vitamin B12 (also known as cobalamin) deficiency and MS produce similar neurological symptoms, including numbness or tingling in hands and feet, vision loss, difficulty walking or speaking normally and cognitive dysfunction, such as problems with memory.
In a new study, published online December 8, 2023 in Cell Reports, researchers at Sanford Burnham Prebys, with collaborators elsewhere, describe a novel molecular link between vitamin B12 and MS that takes place in astrocytes – important non-neuronal glial cells in the brain.
The findings by senior study author Jerold Chun, M.D., Ph.D., professor and senior vice president of neuroscience drug discovery, and Yasuyuki Kihara, Ph.D., research associate professor and co-corresponding author, and colleagues suggest new ways to improve the treatment of MS through CNS-B12 supplementation.
“The shared molecular binding of the brain’s vitamin B12 carrier protein, known as transcobalamin 2 or TCN2, with the FDA-approved MS drug fingolimod provides a mechanistic link between B12 signaling and MS, towards reducing neuroinflammation and possibly neurodegeneration,” said Chun.
“Augmenting brain B12 with fingolimod or potentially related molecules could enhance both current and future MS therapies.”
In their paper, the team at Sanford Burnham Prebys, with collaborators at University of Southern California, Juntendo University in Japan, Tokyo University of Pharmacy and Life Sciences and State University of New York, focused on the molecular functioning of FTY720 or fingolimod (Gilenya®), a sphingosine 1-phosphate (S1P) receptor modulator that suppresses distribution of T and B immune cells errantly attacking the brains of MS patients.
Working with an animal model of MS as well as human post-mortem brains, the researchers found that fingolimod suppresses neuroinflammation by functionally and physically regulating B12 communication pathways, specifically elevating a B12 receptor called CD320 needed to take up and use needed B12 when it is bound to TCN2, which distributes B12 throughout the body, including the CNS.
This known process was newly identified for its interactions with fingolimod within astrocytes. Importantly, the relationship was also observed in human MS brains.
Of particular note, the researchers reported that lower levels of CD320 or dietary B12 restriction worsened the disease course in an animal model of MS and reduced the therapeutic efficacy of fingolimod, which occurred through a mechanism in which fingolimod hitchhikes by binding to the TCN2-B12 complex, allowing delivery of all to the astrocytes via interactions with CD320, with component losses disrupting the process and worsening disease.
These new findings further support to the use of B12 supplementation – especially in terms of delivering the vitamin to astrocytes within the brain – while revealing that fingolimod can correct the impaired astrocyte-B12 pathway in people with MS.
The scientists said it is possible that other S1P receptor modulators on the market, such as Mayzent®, Zeposia® and Ponvory®, may access at least parts of this CNS mechanism. The study supports B12 supplementation with S1P receptor modulators with the goal of improving drug efficacy for this class of medicines.
The study also opens new avenues on how the B12-TCN2-CD320 pathway is regulated by sphingolipids, specifically sphingosine, a naturally occurring and endogenous structural analog of fingolimod, toward improving future MS therapies, Chun said.
“It supports creating brain-targeted B12 formulations. In the future, this mechanism might also extend to novel treatments of other neuroinflammatory and neurodegenerative conditions.”
Additional authors on the study include Deepa Jonnalagadda, Manisha Ray, Clayton Ellington and Richard Rivera, all at Sanford Burnham Prebys, Aran Groves, Sanford Burnham Prebys and UC San Diego; Arjun Saha, University of Southern California; Hyeon-Cheol Lee-Okada and Takehiko Yokomizo, Juntendo University; Tomomi Furihata, Tokyo University of Pharmacy and Life Sciences; Edward V. Quadros, SUNY-Downstate Medical Center.
Funding: The study was supported by a grant from the National Institute of Neurological Disorders and Stroke at the National Institutes of Health (R01NS103940), Novartis, MEXT/JSPS KAKENHI (18H02627, 19KK0199, 21H04798, 18K16246 and 21K08565 ). Further support was provided by the Uehara Memorial Foundation, Kanae Foundation for the Promotion of Medical Science, Mochida Memorial Foundation for Medical and Pharmaceutical Research and the Human Frontier Science Program, plus the Medical Scientist Training Program and Pharmacology Training Grant at UC San Diego (T32GM007752).
About this multiple sclerosis research news
Author: Susan Gammon
Source: Sanford Burnham Prebys
Contact: Susan Gammon – Sanford Burnham Prebys
Image: The image is credited to Neuroscience News
Original Research: Open access.
“FTY720 requires vitamin B12-TCN2-CD320 signaling in astrocytes to reduce disease in an animal model of multiple sclerosis” by Jerold Chun et al. Cell Reports
Abstract
FTY720 requires vitamin B12-TCN2-CD320 signaling in astrocytes to reduce disease in an animal model of multiple sclerosis
Highlights
- CD320 expression is suppressed in MS and EAE astrocytes
- S1P1 inhibition upregulates CD320 expression in astrocytes
- Fingolimod and sphingosine directly bind to TCN2
- Fingolimod-bound TCN2 promotes CD320 internalization in astrocytes
Summary
Vitamin B12 (B12) deficiency causes neurological manifestations resembling multiple sclerosis (MS); however, a molecular explanation for the similarity is unknown. FTY720 (fingolimod) is a sphingosine 1-phosphate (S1P) receptor modulator and sphingosine analog approved for MS therapy that can functionally antagonize S1P1.
Here, we report that FTY720 suppresses neuroinflammation by functionally and physically regulating the B12 pathways. Genetic and pharmacological S1P1 inhibition upregulates a transcobalamin 2 (TCN2)-B12 receptor, CD320, in immediate-early astrocytes (ieAstrocytes; a c-Fos-activated astrocyte subset that tracks with experimental autoimmune encephalomyelitis [EAE] severity).
CD320 is also reduced in MS plaques. Deficiency of CD320 or dietary B12 restriction worsens EAE and eliminates FTY720’s efficacy while concomitantly downregulating type I interferon signaling. TCN2 functions as a chaperone for FTY720 and sphingosine, whose complex induces astrocytic CD320 internalization, suggesting a delivery mechanism of FTY720/sphingosine via the TCN2-CD320 pathway.
Taken together, the B12-TCN2-CD320 pathway is essential for the mechanism of action of FTY720.
